FURTHER FATE OF AMINO ACIDS 113 



Apparently arginine is the only amino acid with more 

 than five carbon atoms which furnishes glucose freely. 

 In this case it is probable that the sugar comes from 

 the ornithine moiety with five carbon atoms, into which 

 it may be converted by the action of arginase. Lysine 

 is the only straight chain amino acid derivative of 

 protein which fails to yield sugar. Although the rela- 

 tionship of the remaining amino acids to carbohydrate 

 metabolism is less definitely established, Lusk has 

 made the interesting calculation that in diabetes sugar 

 may arise from protein to the extent of nearly 60 per 

 cent. He says, "It becomes evident that there may 

 be a condition of nutrition in which protein is used 

 neither for repair nor for growth, but simply to be 

 diaminized and subsequently to act like fat or carbo- 

 hydrate as nutritive materials for the organism." 



2. The Formation of Amino Acids from Carbo- 

 hydrates 



The formation of amino acids from carbohydrate 

 material is a reaction less well known than the reverse 

 process. The close relationship existing between lactic 

 acid and carbohydrates on the one hand and lactic acid 

 and alanine on the other suggests the ready trans- 

 formation of glycogen to alanine presumably with 

 lactic acid and ammonium pyruvate as intermediary 

 products. With this suggestion in mind Embden per- 

 fused a liver rich in glycogen and found that alanine 

 was formed. When, however, perfusion of a glycogen- 



